I've had them both. I currently run the DJ kit. But when I bought the DJ kit there was another problem with my floats and I didn't know it until after installing the DJ kit. So I can't say anythings wrong with the Vito kit. The Vito kit is nice because it comes with the air mixture screws.
I just installed the Vito's kit last weekend on my 01 660 after my rebuild. The extended fuel screws are a necessity when tuning IMO. Shipping was very fast also... I ordered straight from Vito's Performance. I can't say anything about Dynojet... no experience here.
If you paid 90 bucks for any jet kit you got ripped off. There is 8 of them for sale on ebay for under 65 buck. 3 of them have free shipping.
I would run a dynojet over a vito's. They have put time and money to R&D their kit. They build dynoes. I am sure they found some time to run different combos on the a dyno. The dynojet kit also comes with different slide springs.
FMF, K&N, Moose are all relables dynojet kits.
A genuine Yamaha GYTR would be my other option.
The fuel screws is was sells vitos kit. I dont have a problem adjusting the OEM fuel screws with a cordless drill / screwdrive straight screw dirver bit.
I run the Vito's kit...I love the extended fuel screws after trying to adj the stock screws with a right angle bit driver I torqued the tip right off one lodging in the carb which is NOT fun to get out...I didn't realize it was broke until pulled the carbs to install the Vito's screws.
Dynojet's has the equivilant jets of any mikuni jet kit.
A 148dj main is in the neighborhood of a 165 mikuni. There is no guessing game if you know how to properly jet a pair of carbs. It is trial and error. I would see it being a guessing game if you just want to get on here and ask "what jets do I use" and slap in what everybody says to use and call it good.